Motor-pump system for preventing a vapor lock

ABSTRACT

The impeller of a pump is driven by the armature of a motor for pumping a liquid. In response to the onset of vapor bubble formation in the liquid, the impeller load decreases thereby decreasing the armature current and increasing the impeller speed to initiate the establishment of a vapor lock condition in the pump. A relay includes a winding responsive to the decrease in the armature current at the onset of vapor bubble formation in the liquid to open a set of contacts for switching a resistor in series with the motor armature. The resistor decreases the armature voltage thereby decreasing the impeller speed and increasing the impeller load to terminate the establishment of a vapor lock condition in the pump.

United States Patent MacManus [4 1 Oct. 15, 1974 [75] Inventor: DanielC. MacManus, Owosso,

Mich.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Sept. 24, 1973 [21] Appl. No.: 399,994

[52] US. Cl. 417/45, 318/349 [51] Int. Cl. F04b 49/00 [58] Field ofSearch 417/42, 43, 44, 45; 318/322, 349

[56] References Cited UNITED STATES PATENTS 2,366,830 l/l945 Cannon etal. 318/349 2,395,657 2/1946 Dinsmore et al. 417/45 3,026,928 3/1962Phillips et al. 417/45 3,644,300 7/1953 Watermann 3,801,889 4/1974 Quinn417/38 Primary ExaminerWilliam L. Freeh Attorney, Agent, or FirmT. G.Jagodzinski 5 7 ABSTRACT The impeller of a pumpis driven by the armatureof a motor for pumping a liquid. In response to the onset of vaporbubble formation in the liquid, the impeller load decreases therebydecreasing the armature current and increasing the impeller speed toinitiate the establishment of a vapor lock condition in the pump. Arelay includes a winding responsive to the decrease in the armaturecurrent at the onset of vapor bubble formation in the liquid to open aset of contacts for switching a resistor in series with the motorarmature. The resistor decreases the armature voltage thereby decreasingthe impeller speed and increasing the impeller load to terminate theestablishment of a vapor lock condition in the pump.

2 Claims, 1 Drawing Figure MOTOR-PUMP SYSTEM FOR PREVENTING A VAPOR LOCKDISCLOSURE This invention relates to a motor-pump system for preventingthe occurrence of a vapor lock condition in the pump.

According to one aspect of the invention, a pump includes a pump chamberhaving an inlet and an outlet. A pump impeller is rotatably mountedwithin the chamber for drawing liquid into the chamber through the inletand for pumping liquid out of the chamber through the outlet. The loadon the pump is directly related to the density of the liquid. In theabsence of vapor bubble formation, the density of the liquid issubstantially constant at a maximum level. However, at the onset ofvapor bubble formation, the density of the liquid decreases therebydecreasing the load on the impeller. Where the liquid is a highlyvolatile petroleum fuel of the type used in the internal combustionengine of an automotive vehicle, vapor bubbles are readily formed as thetemperature of the fuel increases.

In another aspect of the invention, a motor includes an armature shaftand an armature winding for rotatably driving the armature shaft. Theoperating characteristics of the motor are such that the current throughthe armature winding is directly related to the load on the armatureshaft and the speed of the armature shaft is directly related to thevoltage across the armature winding and is inversely related to the loadon the armature shaft. Preferably, the motor is of the type having apermanent magnet field.

As contemplated by a further aspect of the invention, the armature shaftof the motor is coupled with the impeller of the pump for rotatablydriving the impeller.

When the load on the impeller is substantially constant at a maximumlevel in response to the absence of vapor bubble formation inthe liquid,the load on the armature shaft is likewise at a maximum level tomaintain the current through the armature winding at a maximum level andto maintain the speed of the armature shaft at a minimum level. However,when the load on the impeller decreases in response to the onset ofvapor bubble formation in the liquid, the load on the armature shaftlikewise decreases to decrease the current through the armature windingand to increase the speed of the armature shaft. In response to theincrease in the speed of the armature shaft, the speed of the impellerincreases to initiate a regenerative speed increase/load decreasereaction on the impeller which, if left to continue, would eventuallydevelop a vapor lock condition about the inlet of the pump chamberthereby preventing the entry of fuel into the chamber. Where the pump issupplying fuel to the internal combustion engine ofan automotivevehicle, a vapor lock condition would disable the vehicle by causing theengine to stall from a lack of fuel.

In yet another aspect of the invention, a relay includes a currentsensor provided by a control winding which is connected in the serieswith the armature winding of the motor. Further, the relay includes apair of contacts connected in parallel across a resistor which is alsoconnected in series with the armature winding of the motor. When thecurrent through the armature winding is at a maximum level in responseto the absence of vapor bubble formation in the liquid, the currentsensor closes the contacts so as to bypass the resistor thereby tomaintain the voltage across the armature winding at a maximum level inresponse to the absence of vapor bubble formation in the liquid.COnversely, when the current through the armature winding decreases inresponse to the onset of vapor bubble formation in the liquid, thecurrent sensor opens the contacts so as to not bypass the resistorthereby decreasing the voltage across the armature winding to decreasethe speed of the armature shaft. In response to the decrease in thespeed of the armature shaft, the speed of the impeller decreases toterminate the regenerative speed increase/load decrease reaction on theimpeller so as to prevent the development of a vapor lock conditionabout the inlet of the pump chamber there-by permitting the entry offuel into the chamber to increase the load on the impeller back to themaximum level.

These and other aspects and advantages of the invention will be bestunderstood by reference to the following detailed description of apreferred embodiment when considered in conjunction with theaccompanying drawing.

In the drawing, the sole FIGURE is a schematic diagram of a motor-pumpsystem incorporating the principles of the invention for preventing theoccurrence of a vapor lock condition in the pump.

Referring to the drawing, a pump 10 includes a housing which forms apump chamber 12 having an inlet 14 and an outlet 16. A pump impeller 18is rotatably mounted within the chamber 12 for drawing liquid into thechamber 12 through the inlet 14 and for pumping liquid out of thechamber 12 through the outlet 16 when the impeller 18 is rotatablydriven in a clockwise direction. As an example, the pump 10 may beutilized to supply fuel to the internal combustion engine of anautomotive vehicle. In such event, the inlet 14 would be immersed withinthe fuel stored in the fuel tank of the vehicle while the outlet 16would be coupled to the vehicle engine.

The load on the impeller 18 of the pump 10 is directly related to thedensity of the liquid passing through the pump 10. In the absence ofvapor bubble formation in the liquid, the density of the liquid issubstantially constant at a maximum level so that the load on the pumpis likewise substantially constant at a maximum level. However, at theonset of vapor bubble formation within the liquid, the density of theliquid decreases thereby decreasing the load on the impeller 18. Wherethe liquid is a petroleum fuel which the pump 10 is supplying to theinternal combustion engine of an automotive vehicle, vapor bubbles orpockets are readily formed as the highly volatile fuel undergoes anincrease in temperature.

An electric motor 20 includes an armature shaft 22 and an armaturewinding 24 connected between a pair of contact brushes 26 and 28 forrotatably driving the armature shaft 22 in a clockwise direction whenenergized from a voltage source 30 through a power switch 32. Where thepump 10 is installed within an automotive vehicle, the voltage source 30may be provided by the vehicle storage battery and the power switch 32may be provided by the vehicle ignition switch. The operatingcharacteristics of the motor 20 are such that the current through thearmature winding 24 is directly related to the load on the armatureshaft 22 and the speed of the armature shaft 22 is directly related tothe voltage across the armature winding 24 and is inversely related tothe load on the armature shaft 22. Preferably, the field of the motor 20is provided by a permanent magnet,

The armature shaft 22 of the motor 20 is coupled directly to theimpeller 18 of the pump for rotatably driving the impeller 18 from thearmature shaft 22 such that the load on the impeller 18 is the load onthe armature shaft 22. When the load on the impeller 18 is substantiallyconstant at a maximum level in response to the absence of vapor bubbleformation in the liquid, the load on the armature shaft 22 is likewiseat a maximum level. Accordingly, due to the operating characteristics ofthe motor 20, the current through the armature winding 24 is at amaximum level while the speed of the armature shaft 22 is at a minimumlevel. Alternately, when the load on the impeller 18 decreases inresponse to the onset of vapor bubble formation in the liquid, the loadon the armature shaft 22 likewise decreases. Again, due to the operatingcharacteristics of the motor 20, the current through the armaturewinding 24 decreases while the speed of the armature shaft 22 increasesthereby increasing the speed of the impeller 18.

As the speed of the impeller 18 increases, less liquid and more vapor isable to enter the pump chamber 12 through the inlet 14 because the vaporis more mobile than the liquid. Consequently, the load on the impeller18 further decreases thereby increasing the speed of the impeller 18 tofurther decrease the liquid and increase the vapor entering the pumpchamber 12. If allowed to continue, the eventual consequence of thisregenerative speed increase/load decrease reaction is the development ofa back pressure or vapor lock about the inlet 14 of the pump chamber 12thereby preventing the entry of fuel into the chamber 12. Where the pump10 is supplying fuel to the internal combustion engine of an automotivevehicle, the development of a vapor lock condition about the inlet 14 ofthe pump chamber 12 would disable the vehicle by causing the engine tostall from a lack of fuel.

in order to prevent the occurrence of a vapor lock condition in the pump10., an anti-vapor lock arrange ment is provided by a resistor 34 and arelay 36. The resistor 34 is connected in a series circuit with thearmature winding 24 of the motor 20 for reducing the voltage across thearmature winding 24 when the resistor 34 is not bypassed. Specifically,the voltage across the armature winding 24 is reduced by an amount equalto the voltage across the resistor 34.

The relay 36 includes a current sensor provided by a control winding 38and a set of switching contacts provided by a pair of flexible andmagnetizable reeds 40 and 42 which are electromagnetically coupled withthe control winding 38. The contacts 40 and 42 are normally disposed inan opened position and are electromagnetically operable to a closedposition against an inherent spring bias tending to return them to theopened position. In the usual manner, the reeds 40 and 42 are enclosedwithin an evacuated envelope 44 to ensure their sensitivity anddurability. The control winding 38 is connected in series with thearmature winding 24 of the motor 20. The switching contacts 40 and 42are connected in parallel across the resistor 34.

When the current through the armature winding 24 of the motor 20 is at amaximum level in response to the absence of vapor bubble formation inthe liquid, the electromagnetic field developed by the flow of thearmature current through the control winding 38 is sufficient toovercome the spring bias of the switching contacts 40 and 42 which closeso that the resistor 34 is bypassed. With the resistor 34 bypassed, thevoltage across the armature winding 24 of the motor 20 is maintained ata maximum level thereby to maintain the speed of the armature shaft 22and the speed of the impeller 18 at a maximum level.

When the current through the armature winding 24 of the motor 20decreases in response to the initiation of vapor bubble formation in theliquid, the electromagnetic field developed by the flow ofthe armaturecurrent through the control winding 38 is insufficient to overcome thespring bias of the switching contacts which open so that the resistor 34is not bypassed. With the resistor 34 not bypassed, the voltage acrossthe armature winding 24 of the motor 20 is decreased to decrease thespeed of the armature shaft 22 and the speed of the impeller 18. As thespeed of the impeller 18 decreases, the regenerative speed increase/loaddecrease reaction on the impeller 18 is terminated to prevent thedevelopment of a vapor lock condition about the inlet 14 of the pumpchamber 12.

Accordingly, more fuel is permitted to enter the pump chamber 12 therebyincreasing the load on the impeller 18 back toward a maximum level. Asthe load on the impeller 18 increases to a maximum level, the currentthrough the armature winding 24 of the motor 20 likewise increases to amaximum level to reclose the contacts 40 and 42 through theelectromagnetic action of the winding 38. With the contacts 40 and 42closed, the resistor 34 is again bypassed.

It will now be appreciated that the foregoing description of a preferredembodiment of the invention is made for demonstrative purposes only andthat various alterations and modifications may be made to theillustrated embodiment without departing from the spirit and scope ofthe invention.

What is claimed is:

1. In combination: a pump including a pump chamber having an inlet andan outlet and a pump impeller rotatably mounted within the chamber fordrawing liquid into the chamber through the inlet and for pumping liquidout of the chamber through the outlet when the impeller is rotatablydriven such that the load on the impeller is directly related to thedensity of the liquid which is substantially constant at a maximum levelin response to the absence of vapor bubble formation and which decreasesin response to the onset of -vapor bubble formation thereby decreasingthe load on the impeller; a motor including an armature shaft and anarmature winding for rotatably driving the armature shaft such that thecurrent through the armature winding is directly related to the load onthe armature shaft and such that the speed of the armature shaft isdirectly related to the voltage across the armature winding and isinversely related to the load on the armature shaft, the armature shaftof the motor coupled with the impeller of the pump for rotatably drivingthe impeller such that when the load on the impeller is substantiallyconstant at a maximum level in response to the absence of vapor bubbleformation in the liquid the load on the armature shaft is likewise at amaximum level to maintain the current through the armature winding at amaximum level and to maintain the speed of the armature shaft at aminimum level and so that when the load on the impeller decreases inresponse to the onset of vapor bubble formation in the liquid the loadon the armature shaft likewise decreases to decrease the current throughthe armature winding and to increase the speed of the armature shaftwhich in turn increases the speed of the impeller thereby initiating aregenerative speed increase/load decrease reaction on the impeller whichif left to continue would lead to the development of a vapor lockcondition about the inlet of the pump chamber so as to prevent the entryof fuel into the chamber; a resistor connected in series with thearmature winding of the motor for reducing the voltage across thearmature winding when the resistor is not bypassed; means responsive tothe current through the armature winding of the motor for bypassing theresistor when the current through the armature winding is at a maximumlevel in response to the absence of vapor bubble formation in the liquidto maintain the voltage across the armature winding at a maximum leveland for not bypassing the resistor when the current through the armaturewinding decreases due to the onset of vapor bubble formation in theliquid to increase the speed of the armature shaft which in turndecreases the speed of the impeller thereby terminating the regenerativespeed increase/load decrease reaction on the impeller to prevent thedevelopment of a vapor lock condition about the inlet ofthe pump chamberso as to permit the entry of fuel into the chamber to increase the loadon the impeller back to the maximum level.

2. In combination: a pump including a pump cham her having an inlet andan outlet and a pump impeller rotatably mounted within the chamber fordrawing liquid into the chamber through the inlet and for pumping liquidout of the chamber through the outlet when the impeller is rotatablydriven such that the load on the impeller is directly related to thedensity of the liquid which is substantially constant at a maximum levelin response to the absence of vapor bubble formation and which decreasesin response to the onset of vapor bubble formation thereby decreasingthe load on the impeller; a motor including an armature shaft and anarmature winding for rotatably driving the armature shaft such that thecurrent through the armature winding is directly related to the load onthe armature shaft and such that the speed of the armature shaft isdirectly related to the voltage across the armature winding and isinversely related to the load on the armature shaft, the armature shaftof the motor coupled with the impeller of the pump for rotatably drivingthe impeller such that when the load on the impeller is substantiallyconstant at a maximum level in response to the absence of vapor bubbleformation in the liquid the load on the armature shaft is likewise at amaximum level to maintain the current through the armature winding at amaximum level and to maintain the speed of the armature shaft at aminimum level and so that when the load on the impeller decreases inresponse to the onset of vapor bubble formation in the liquid the loadon the armature shaft likewise decreases to decrease the current throughthe armature winding and to increase the speed of the armature shaftwhich in turn increases the speed of the impeller thereby initiating aregenerative speed increase/load decrease reaction on the impeller whichif left to continue would lead to the development of a vapor lockcondition about the inlet of the pump chamber so as to prevent the entryof fuel into the chamber; a resistor connected in series with thearmature winding of the motor for reducing the voltage across thearmature winding when the resistor is not bypassed; a relay including apair of switching contacts connected across the resistor and a currentsensor connected in series with the armature winding of the motor forclosing the contacts so that the resistor is bypassed when the currentthrough the armature winding is at a maximum level in response to theabsence of vapor bubble formation in the liquid to maintain the voltageacross the armature winding at a maximum level and for opening thecontacts so that the resistor is not bypassed when the current throughthe armature winding decreases due to the onset of vapor bubbleformation in the liquid to increase the speed ofthe armature shaft whichin turn decreases the speed of the impeller thereby terminating theregenerative speed increase/- load decrease reaction on the impeller toprevent the development of a vapor lock condition about the inlet of thepump chamber so as to permit the entry of fuel into the chamber toincrease the load on the impeller

1. In combination: a pump including a pump chamber having an inlet andan outlet and a pump impeller rotatably mounted within the chamber fordrawing liquid into the chamber through the inlet and for pumping liquidout of the chamber through the outlet when the impeller is rotatablydriven such that the load on the impeller is directly related to thedensity of the liquid which is substantially constant at a maximum levelin response to the absence of vapor bubble formation and which decreasesin response to the onset of vapor bubble formation thereby decreasingthe load on the impeller; a motor including an armature shaft and anarmature winding for rotatably driving the armature shaft such that thecurrent through the armature winding is directly related to the load onthe armature shaft and such that the speed of the armature shaft isdirectly related to the voltage across the armature winding and isinversely related to the load on the armature shaft, the armature shaftof the motor coupled with the impeller of the pump for rotatably drivingthe impeller such that when the load on the impeller is substantiallyconstant at a maximum level in response to the absence of vapor bubbleformation in the liquid the load on the armature shaft is likewise at amaximum level to maintain the current through the armature winding at amaximum level and to maintain the speed of the armature shaft at aminimum level and so that when the load on the impeller decreases inresponse to the onset of vapor bubble formation in the liquid the loadon the armature shaft likewise decreases to decrease the current throughthe armature winding and to increase the speed of the armature shaftwhich in turn increases the speed of the impeller thereby initiating aregenerative speed increase/load decrease reaction on the impeller whichif left to continue would lead to the development of a vapor lockcondition about the inlet of the pump chamber so as to prevent the entryof fuel into the chamber; a resistor connected in series with thearmature winding of the motor for reducing the voltage across thearmature winding when the resistor is not bypassed; means responsive tothe current through the armature winding of the motor for bypassing theresistor when the current through the armature winding is at a maximumlevel in response to the absence of vapor bubble formation in the liquidto maintain the voltage across the armature winding at a maximum leveland for not bypassing the resistor when the current through the armaturewinding decrEases due to the onset of vapor bubble formation in theliquid to increase the speed of the armature shaft which in turndecreases the speed of the impeller thereby terminating the regenerativespeed increase/load decrease reaction on the impeller to prevent thedevelopment of a vapor lock condition about the inlet of the pumpchamber so as to permit the entry of fuel into the chamber to increasethe load on the impeller back to the maximum level.
 2. In combination: apump including a pump chamber having an inlet and an outlet and a pumpimpeller rotatably mounted within the chamber for drawing liquid intothe chamber through the inlet and for pumping liquid out of the chamberthrough the outlet when the impeller is rotatably driven such that theload on the impeller is directly related to the density of the liquidwhich is substantially constant at a maximum level in response to theabsence of vapor bubble formation and which decreases in response to theonset of vapor bubble formation thereby decreasing the load on theimpeller; a motor including an armature shaft and an armature windingfor rotatably driving the armature shaft such that the current throughthe armature winding is directly related to the load on the armatureshaft and such that the speed of the armature shaft is directly relatedto the voltage across the armature winding and is inversely related tothe load on the armature shaft, the armature shaft of the motor coupledwith the impeller of the pump for rotatably driving the impeller suchthat when the load on the impeller is substantially constant at amaximum level in response to the absence of vapor bubble formation inthe liquid the load on the armature shaft is likewise at a maximum levelto maintain the current through the armature winding at a maximum leveland to maintain the speed of the armature shaft at a minimum level andso that when the load on the impeller decreases in response to the onsetof vapor bubble formation in the liquid the load on the armature shaftlikewise decreases to decrease the current through the armature windingand to increase the speed of the armature shaft which in turn increasesthe speed of the impeller thereby initiating a regenerative speedincrease/load decrease reaction on the impeller which if left tocontinue would lead to the development of a vapor lock condition aboutthe inlet of the pump chamber so as to prevent the entry of fuel intothe chamber; a resistor connected in series with the armature winding ofthe motor for reducing the voltage across the armature winding when theresistor is not bypassed; a relay including a pair of switching contactsconnected across the resistor and a current sensor connected in serieswith the armature winding of the motor for closing the contacts so thatthe resistor is bypassed when the current through the armature windingis at a maximum level in response to the absence of vapor bubbleformation in the liquid to maintain the voltage across the armaturewinding at a maximum level and for opening the contacts so that theresistor is not bypassed when the current through the armature windingdecreases due to the onset of vapor bubble formation in the liquid toincrease the speed of the armature shaft which in turn decreases thespeed of the impeller thereby terminating the regenerative speedincrease/load decrease reaction on the impeller to prevent thedevelopment of a vapor lock condition about the inlet of the pumpchamber so as to permit the entry of fuel into the chamber to increasethe load on the impeller back to the maximum level.